JP2006030748A - Projection display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type display device capable of suppressing display with floating black and realizing high contrast.
A projection display device including a light modulation unit, the light modulation unit having a negative dielectric anisotropy liquid crystal layer 80 having a pretilt and a refractive index anisotropy in an optical axis direction. When the refractive index in the azimuth direction orthogonal to each other in the plane is nx and ny and the refractive index in the thickness direction is nz, nz <nx Alternatively, nz <ny is satisfied, and the optical compensator 92 has an in-plane retardation when nx> ny is satisfied, and the slow axis 92a of the in-plane retardation is the orientation of the pretilt of the liquid crystal layer 80. It is characterized by being substantially perpendicular to the angular direction.
[Selection] Figure 5

Description

  The present invention relates to a projection display device.

Conventionally, as a liquid crystal device, there is known a liquid crystal device that is driven by a “VA (Vertical Alignment) mode” in which a liquid crystal having a negative dielectric anisotropy is aligned perpendicularly to a substrate and is tilted by applying a voltage.
As such a liquid crystal device, a configuration in which a retardation plate and a liquid crystal layer are arranged between two polarizing plates is known, and the retardation plate has a slow axis parallel to the crossed Nicols of the polarizing plate. Generally, it is arranged so as to be vertical (see, for example, Patent Document 1). By adopting such a configuration, it is possible to display an ideal black color without being influenced by the phase difference.

On the other hand, in recent years, a projection display device (liquid crystal projector) has been put into practical use as a display device capable of displaying a large screen. In such a projection display device, a configuration has been proposed in which a liquid crystal device including the vertical alignment liquid crystal is provided as a light valve.
JP-A-11-95208

By the way, the present inventor has found that if the liquid crystal device described in the above-mentioned patent document is simply applied to a projection display device, a black display is generated and the contrast is lowered.
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a projection display device that can suppress the display of black floating and realize high contrast.

The present inventor generally gives a pretilt to define the direction in which the liquid crystal molecules tilt in the vertically aligned liquid crystal, but in this case, a phase difference occurs in the azimuth direction of the pretilt and black is floated. It has been found that the contrast is reduced due to the display.
Therefore, the present inventor has come up with the present invention having the following means based on the above.

That is, the projection type display device of the present invention has nz <nx and refractive indices in two azimuth directions orthogonal to each other in a plane are defined as nx and ny, and a refractive index in the thickness direction is defined as nz. An optical compensator having an optical axis satisfying nz <ny and having an in-plane retardation satisfying nx> ny, and an azimuth angle direction substantially perpendicular to the direction of the slow axis of the in-plane retardation And a light modulation means including a liquid crystal layer with negative dielectric anisotropy having a pretilt.
By providing such an optical compensation plate, it is possible to cancel the phase difference of the vertically aligned liquid crystal initially having a pretilt and to optically compensate for the phase difference. As a result, display with black floating can be suppressed, and high contrast can be realized.

In the above projection type display device, the in-plane phase difference is 20 nm or less.
Thus, by setting the in-plane retardation to 20 nm or less, the retardation of the liquid crystal layer having a pretilt of 80 ° or more can be compensated.

In the projection display device, the alignment film for aligning the liquid crystal layer is made of an inorganic material.
Thus, by using an inorganic material as the alignment film, the liquid crystal layer can be aligned so that the vertically aligned liquid crystal molecules have a predetermined pretilt. As the inorganic material, SiO _x (x = 1 or 2) Al ₂ O ₃ or the like is assumed.

In the projection display device, the light modulation unit includes a first polarizing plate provided on the light incident side of the liquid crystal layer and a second polarizing plate provided on the light emission side of the liquid crystal layer. And the optical compensation plate is disposed between the liquid crystal layer and the first polarizing plate, or between the liquid crystal layer and the second polarizing plate.
In this way, the phase difference of the vertically aligned liquid crystal initially having a pretilt is canceled between the liquid crystal layer and the first polarizing plate or between the liquid crystal layer and the second polarizing plate. The phase difference can be optically compensated.

In the above projection type display device, an antireflection film is formed on the surface of the optical compensation plate.
In this way, it is possible to suppress light leakage caused by light entering the light modulation means.

(Projection type display device)
Hereinafter, a first embodiment of a projection display device of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a main part of a projection display device.
As shown in FIG. 1, the projection display device PJ includes a light source 10, a uniform illumination system 20 that uniformizes the luminance distribution of light incident from the light source 10, and a wavelength region of light incident from the uniform illumination system 20. Color modulator 25 (including three transmissive liquid crystal light valves 22, 23, and 24 as light modulating means) for modulating the luminance of the three primary colors of RGB, and light incident from the color modulator 25 on a screen (not shown) And a projection lens 27 that projects onto the projector.

  The light source 10 includes a lamp 11 such as an ultrahigh pressure mercury lamp or a xenon lamp, and a reflector 12 that reflects and collects light emitted from the lamp 11.

The uniform illumination system 20 includes two lens arrays 21 and 22 made of fly-eye lenses, a polarization conversion element 23, and a condenser lens 24. Then, the luminance distribution of the light from the light source 10 is made uniform by the two lens arrays 21 and 22, and the uniformed light is polarized by the polarization conversion element 23 in the polarization direction in which the color modulation unit can be incident, and the polarized light is condensed. The light is condensed by the lens 24 and emitted to the color modulation unit 25.
The polarization conversion element 23 is composed of, for example, a PBS array and a half-wave plate, and converts random polarization into specific linear polarization.

  The color modulation unit 25 includes two dichroic mirrors 13 and 14 as light separation means, three mirrors (reflection mirrors 15, 16, and 17), and five field lenses (lens 18a, relay lens 18b, and collimating lens 26B). , 26G, 26R), three liquid crystal light valves 22, 23, 24, and a cross dichroic prism 28.

  The dichroic mirrors 13 and 14 separate (spread) the light (white light) from the light source 10 into red (R), green (G), and blue (B) RGB three primary color lights. The dichroic mirror 13 is formed by reflecting a B light and a G light on a glass plate or the like and forming a dichroic film having a property of transmitting the R light. The white light from the light source 10 is included in the white light. Reflects light and G light and transmits R light. The dichroic mirror 14 is formed by forming a dichroic film that reflects G light on a glass plate or the like and transmits B light. Of the G light and B light transmitted through the dichroic mirror 13, the dichroic mirror 14 reflects G light. The light is transmitted to the collimating lens 26G, and the blue light is transmitted to the lens 18a.

  The relay lens 18b transmits light (light intensity distribution) in the vicinity of the lens 18a to the vicinity of the collimating lens 26B, and the lens 18a has a function of efficiently making light incident on the relay lens 18b. The B light incident on the lens 18a is transmitted to the liquid crystal light valve 24 which is spatially separated, with its intensity distribution almost preserved and almost no light loss.

  The collimating lenses 26B, 26G, and 26R substantially parallelize each color light incident on the corresponding liquid crystal light valves 22, 23, and 24 to narrow the angle distribution of the incident light, thereby improving the display characteristics of the liquid crystal light valves 22, 23, and 24. It has a function to make it. Then, the RGB three primary color light beams dispersed by the dichroic mirrors 13 and 14 are transmitted to the above-described mirrors (reflecting mirrors 17, 15, and 16) and field lenses (lens 18a, relay lens 18b, collimating lenses 26B, 26G, and 26R). Through the liquid crystal light valves 22, 23 and 24.

  The liquid crystal light valves 22, 23, and 24 include a glass substrate on which pixel electrodes and switching elements such as thin film transistors and thin film diodes for driving the pixel electrodes are formed in a matrix, and a glass substrate on which a common electrode is formed over the entire surface. An active matrix type liquid crystal display element in which a vertically aligned liquid crystal is sandwiched between them and a polarizing plate and a C plate are arranged (described later).

  The liquid crystal light valves 22, 23, 24 are driven in a normally black mode in which a black / dark (non-transmission) state is applied when a non-selection voltage is applied and a white / bright (transmission) state is applied when a selection voltage is applied. The gradation between light and dark is analog controlled according to the control value. The liquid crystal light valve 24 modulates the incident B light based on the display image data, and emits modulated light containing an optical image. The liquid crystal light valve 23 modulates the incident G light based on the display image data, and emits modulated light including an optical image. The liquid crystal light valve 22 optically modulates the incident R light based on the display image data, and emits modulated light including an optical image.

  The cross dichroic prism 28 has a structure in which four right-angle prisms are bonded to each other, and a dielectric multilayer film that reflects B light (B light reflecting dichroic film 28B) and a dielectric multilayer film that reflects R light are included therein. (R light reflecting dichroic film 28R) is formed in an X-shaped cross section. Then, the G light from the liquid crystal light valve 23 is transmitted, the R light from the liquid crystal light valve 22 and the B light from the liquid crystal light valve 24 are bent, and these three colors of light are combined to form a color image. .

  The projection lens 27 projects an optical image formed on the display surface of the liquid crystal light valve 100 onto a screen (not shown) to display a color image.

  The liquid crystal light valves 22, 23, and 24 have a function of modulating the intensity of transmitted light and including an optical image corresponding to the degree of modulation. The liquid crystal light valves 22, 23, and 24 modulate light in a specific wavelength region (colored light such as R, G, and B) dispersed by the dichroic mirrors 13 and 14, which are light separation means.

Next, the overall light transmission flow of the projection display device PJ will be described.
The white light from the light source 10 is split into three primary colors of red (R), green (G), and blue (B) by the dichroic mirrors 13 and 14, and lenses and mirrors including the collimating lenses 26B, 26G, and 26R. Through the liquid crystal light valve 22, 23, 24. Each color light incident on the liquid crystal light valves 22, 23, 24 is color-modulated based on external data corresponding to each wavelength region, and is emitted as modulated light including an optical image. Each modulated light from the liquid crystal light valves 22, 23, 24 is incident on the cross dichroic prism 28, where it is combined into one light and emitted to the projection lens 27. Then, the projection lens 27 projects the final combined light from the liquid crystal light valve 100 onto a screen (not shown) to display a desired image.

(First embodiment of liquid crystal light valve)
Next, with reference to FIGS. 2 to 6, the liquid crystal light valves (light modulation means) 22, 23, and 24 included in the projection display device will be described. Here, the liquid crystal light valve 22 will be described as a representative, and the description of the liquid crystal light valves 23 and 24 will be omitted.
The liquid crystal light valve 22 includes a liquid crystal panel in which a liquid crystal layer is sandwiched between a pair of substrates, and a C plate (optical compensation plate) and a polarizing plate outside the liquid crystal panel. In the present embodiment, an active matrix type liquid crystal light valve using a thin film transistor (hereinafter referred to as TFT) element as a switching element will be described.
In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.
In the present specification, the liquid crystal layer side of each component of the liquid crystal light valve is referred to as the inner side, and the opposite side is referred to as the outer side. “When a non-selection voltage is applied” and “when a selection voltage is applied” are respectively “when the applied voltage to the liquid crystal layer is close to the threshold voltage of the liquid crystal” and “the applied voltage to the liquid crystal layer is It means “when sufficiently high compared to the threshold voltage”.

FIG. 2 is an equivalent circuit diagram of the liquid crystal panel.
Pixel electrodes 39 are formed on a plurality of dots arranged in a matrix to form an image display area of the liquid crystal panel. Further, on the side of the pixel electrode 39, a TFT element 60, which is a switching element for controlling energization of the pixel electrode 39, is formed. A data line 36 a is electrically connected to the source of the TFT element 60. Image signals S1, S2,..., Sn are supplied to each data line 36a. The image signals S1, S2,..., Sn may be supplied to each data line 36a in this order, or may be supplied for each group to a plurality of adjacent data lines 36a. .

  In addition, the scanning line 63 a is electrically connected to the gate of the TFT element 60. The scanning signals G1, G2,..., Gm are supplied to the scanning line 63a in a pulse manner at a predetermined timing. The scanning signals G1, G2,..., Gm are applied sequentially to each scanning line 63a in this order. In addition, the pixel electrode 39 is electrically connected to the drain of the TFT element 60. When the TFT element 60 serving as a switching element is turned on for a certain period by the scanning signals G1, G2,..., Gm supplied from the scanning line 63a, the image signals S1, S2,. , Sn are written into the liquid crystal of each pixel at a predetermined timing.

  Image signals S1, S2,..., Sn written in the liquid crystal are held for a certain period by a liquid crystal capacitor formed between the pixel electrode 39 and a common electrode described later. In order to prevent the stored image signals S1, S2,..., Sn from leaking, a storage capacitor 47 is formed between the pixel electrode 39 and the capacitor line 33b, and is arranged in parallel with the liquid crystal capacitor. . Thus, when a voltage signal is applied to the liquid crystal, the alignment state of the liquid crystal molecules changes depending on the applied voltage level. As a result, the light incident on the liquid crystal is modulated to enable gradation display.

FIG. 3 is an explanatory diagram of a planar structure of the liquid crystal panel.
In the liquid crystal panel of the present embodiment, a rectangular pixel electrode 39 made of a transparent conductive material such as indium tin oxide (hereinafter referred to as ITO) on the TFT array substrate (the outline is indicated by a broken line 39a). Are arranged in a matrix. A data line 36 a, a scanning line 63 a, and a capacitor line 33 b are provided along the vertical and horizontal boundaries of the pixel electrode 39. In the present embodiment, the region in which each pixel electrode 39 is formed is a dot, and the display can be performed for each dot arranged in a matrix.

  The TFT element 60 is formed around a semiconductor layer 31a made of a polysilicon film or the like. A data line 36 a is electrically connected to a source region (described later) of the semiconductor layer 31 a through a contact hole 35. A pixel electrode 39 is electrically connected to the drain region (described later) of the semiconductor layer 31a through a contact hole 38. On the other hand, a channel region 31a 'is formed in a portion of the semiconductor layer 31a facing the scanning line 63a. Note that the scanning line 63a functions as a gate electrode in a portion facing the channel region 31a '.

  The capacitor line 33b is formed from the intersection of the main line portion extending in a substantially straight line along the scanning line 63a (that is, the first region formed along the scanning line 63a in plan view) and the data line 36a. And a projecting portion (that is, a second region extending along the data line 36a in plan view) that projects to the front side (upward in the drawing) along the line 36a. In addition, a first light-shielding film 41a is formed in a region indicated by a diagonal line rising to the right in FIG. Then, the protruding portion of the capacitor line 33b and the first light shielding film 41a are electrically connected through the contact hole 13 to form a storage capacitor to be described later.

4 is an explanatory diagram of a cross-sectional structure of the liquid crystal panel, and is a side cross-sectional view taken along the line AA ′ of FIG.
As shown in FIG. 4, the liquid crystal panel 90 is mainly composed of a TFT array substrate 40, a counter substrate 50 disposed to face the TFT array substrate 40, and a liquid crystal layer 80 sandwiched therebetween. The TFT array substrate 40 is mainly composed of a substrate body 40A made of a light-transmitting material such as glass or quartz, a TFT element 60, a pixel electrode 39, an alignment film 46, and the like formed inside thereof. One counter substrate 50 is mainly composed of a substrate body 50A made of a translucent material such as glass or quartz, and a common electrode 51 and an alignment film 52 formed inside thereof.

  A first light shielding film 41 a and a first interlayer insulating film 42 described later are formed on the surface of the TFT array substrate 40. A semiconductor layer 31a is formed on the surface of the first interlayer insulating film 42, and the TFT element 60 is formed around the semiconductor layer 31a. A channel region 31a 'is formed in a portion of the semiconductor layer 31a facing the scanning line 63a, and a source region and a drain region are formed on both sides thereof. Since the TFT element 60 employs an LDD (Lightly Doped Drain) structure, a high concentration region having a relatively high impurity concentration and a low concentration region (LDD having a relatively low concentration) are respectively provided in the source region and the drain region. Region). That is, a low concentration source region 31b and a high concentration source region 31d are formed in the source region, and a low concentration drain region 31c and a high concentration drain region 31e are formed in the drain region.

  A gate insulating film 32 is formed on the surface of the semiconductor layer 31a. A scanning line 63a is formed on the surface of the gate insulating film 32, and a part thereof constitutes a gate electrode. A second interlayer insulating film 34 is formed on the surfaces of the gate insulating film 32 and the scanning line 63a. A data line 36a is formed on the surface of the second interlayer insulating film 34, and the data line 36a is electrically connected to the high-concentration source region 31d through a contact hole 35 formed in the second interlayer insulating film 34. ing. Further, a third interlayer insulating film 37 is formed on the surfaces of the second interlayer insulating film 34 and the data line 36a. A pixel electrode 39 is formed on the surface of the third interlayer insulating film 37, and the pixel electrode 39 is connected to the high-concentration drain region via a contact hole 38 formed in the second interlayer insulating film 34 and the third interlayer insulating film 37. 31e is electrically connected. Further, an alignment film 46 made of polyimide or the like is formed so as to cover the pixel electrode 39. The surface of the alignment film 46 is rubbed or the like so that the alignment direction of the liquid crystal molecules when a non-selection voltage is applied can be regulated.

  In the present embodiment, the first storage capacitor electrode 31f is formed by extending the semiconductor layer 31a. Further, a dielectric film is formed by extending the gate insulating film 32, and a capacitor line 33b is disposed on the surface thereof to form a second storage capacitor electrode. Thus, the above-described storage capacitor 47 is configured.

  A first light shielding film 41 a is formed on the surface of the TFT array substrate 40 corresponding to the formation region of the TFT element 60. The first light shielding film 41a prevents light incident on the liquid crystal panel from entering the channel region 31a ′, the low concentration source region 31b, and the low concentration drain region 31c of the semiconductor layer 31a. The first light shielding film 41a is electrically connected to the capacitor line 33b at the previous stage or the subsequent stage through the contact hole 13 formed in the first interlayer insulating film. Thus, the first light shielding film 41a functions as a third storage capacitor electrode, and a new storage capacitor is formed between the first storage capacitor electrode 31f using the first interlayer insulating film 42 as a dielectric film.

On the other hand, the second light-shielding film 23 is formed on the surface of the counter substrate 50 corresponding to the formation region of the data line 36a, the scanning line 63a, and the TFT element 60. The second light shielding film 23 prevents light incident on the liquid crystal panel from entering the channel region 31a ′, the low concentration source region 31b, and the low concentration drain region 31c of the semiconductor layer 31a. Further, a common electrode 51 made of a conductor such as ITO is formed on almost the entire surface of the counter substrate 50 and the second light shielding film 23.
Further, an alignment film 52 is formed on the surface of the common electrode 51. The alignment film 52 is formed by depositing an inorganic material such as a silicon oxide film. Such an alignment film 52 regulates the alignment direction of the liquid crystal molecules when a non-selection voltage is applied, and can impart a pretilt to the liquid crystal molecules. In addition, the pretilt in this specification means the angle which a substrate surface and the orientation direction of a liquid crystal molecule make.

A liquid crystal layer 80 is sandwiched between the TFT array substrate 40 and the counter substrate 50. The liquid crystal layer 80 is made of a liquid crystal material having a negative dielectric anisotropy whose initial alignment state is substantially vertical alignment, and has a pretilt. In other words, the direction in which the liquid crystal molecules tilt when the selection voltage is applied is determined.
Further, such a liquid crystal layer 80 has a pretilt when a non-selection voltage is applied, that is, the liquid crystal layer 80 itself has a phase difference. The pretilt is set to 85 ° by the alignment film 52.

5A and 5B are diagrams for explaining the configuration of the liquid crystal light valve 22, in which FIG. 5A is an exploded perspective view, and FIG. 5B is a plan view corresponding to FIG. 5A. .
The liquid crystal light valve 22 of the present embodiment is disposed on the liquid crystal panel 90 described above, the C plate (optical compensation plate) 92 disposed outside the liquid crystal panel 90, the outside of the C plate 92, and the outside of the liquid crystal panel 90. The polarizing plate (first polarizing plate) 93 and the polarizing plate (second polarizing plate) 94 are configured. Here, the polarizing plate 93 is provided on the light incident side of the liquid crystal layer 80, and the polarizing plate 94 is provided on the light emitting side of the liquid crystal layer 80.

  As shown in FIG. 5, a polarizing plate 93 is disposed on the light incident side of the liquid crystal panel 90, and a polarizing plate 94 is disposed on the light emitting side. Each of the polarizing plates 93 and 94 has a function of absorbing linearly polarized light in the absorption axis direction and transmitting linearly polarized light in the transmission axis direction. The polarizing plates 93 and 94 are arranged so that their absorption axes and transmission axes are orthogonal to each other.

  The C plate 92 is a retardation film having a retardation in the thickness direction, and the refractive index (nz) in the thickness direction is smaller than the refractive index (nx, ny) in the azimuth direction in the plane. Has optical properties. That is, nz <nx and nz <ny are established. Further, in the in-plane refractive index, nx> ny is established, and the C plate 92 has an in-plane phase difference, that is, a slow axis 92a. Further, the slow axis 92 a is arranged perpendicular to the pretilt azimuth direction 80 a of the liquid crystal layer 80.

Such a C plate 92 has a configuration in which an antireflection film (antireflection film) is provided on a base material made of triacetylcellulose (hereinafter referred to as a TAC base material) or the like. The TAC base material has an in-plane retardation of 3 to 5 nm in the plane. Specifically, the in-plane retardation of 3 to 5 nm means that the retardation value (nx−ny) · d when the thickness of the C plate 92 is d is 3 to 5 nm.
Further, the C plate 92 has a configuration in which an antireflection film (antireflection film) is formed on the surface of the TAC substrate, and suppresses light leakage of the TFT caused by the incident light L in FIG. .

FIG. 6 is a transmittance characteristic diagram showing the relationship between the wavelength of light transmitted through the liquid crystal light valve 22 and the transmittance when the in-plane retardation of the C plate 92 is varied from 0 to 8 nm.
In FIG. 6, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance. In the figure, P ₀ means a polarizer, which is a transmittance characteristic of only the polarizing plates 93 and 94 and shows an ideal transmittance characteristic.

As shown in FIG. 6, when the in-plane retardation is 0 nm, does not use the C plate 92 in other words, in the case of only the liquid crystal layer 80, whereas the thus away from the polarizer P _0, - plane retardation transmittance characteristic is obtained near the polarizer _{P 0} in the case of 3-5 nm.
Further, it has been confirmed by the present inventor that black display sinks when the tilts of the C plate 92 and the liquid crystal layer 80 are orthogonal to each other, and the contrast is improved to 1500 compared to the conventional 1000.

As described above, in the present embodiment, since the liquid crystal light valve 22 includes the C plate 92, the in-plane retardation of the C plate 92 has an initial pretilt of the vertically aligned liquid crystal layer 80. The phase difference can be canceled and optically compensated. As a result, display with black floating can be suppressed, and high contrast can be realized.
Further, since the alignment film 52 made of an inorganic material is formed, the alignment direction of the liquid crystal molecules when a non-selection voltage is applied can be regulated, and a pretilt can be imparted to the liquid crystal molecules.
In addition, since the C plate 92 is disposed between the polarizing plate 93 and the liquid crystal panel 90, the phase difference of the vertically aligned liquid crystal that initially has a pretilt between the liquid crystal panel 90 and the polarizing plate 93. And the phase difference can be optically compensated. The C plate 92 is not limited to be disposed between the polarizing plate 93 and the liquid crystal panel 90. A configuration in which the C plate 92 is disposed between the polarizing plate 94 and the liquid crystal panel 90 may be employed.
In addition, since the C plate 92 includes an antireflection film formed on the surface of the TAC base material, light leakage caused by light entering the liquid crystal panel 90 can be suppressed.

(Second embodiment of the liquid crystal light valve)
Next, a second embodiment of the liquid crystal light valve will be described with reference to the drawings.
In the present embodiment, the same components as those of the first embodiment described above are denoted by the same reference numerals, and the description will be simplified, and only different portions will be described.
In the liquid crystal light valve of the first embodiment, the liquid crystal layer 80 has a pretilt of 85 ° and a C plate 92 having an in-plane retardation of 3 to 5 nm. However, in the present embodiment, the liquid crystal layer 80 has an angle of 83 °. A C plate 92 having a pretilt and an in-plane retardation of 7 nm is employed.

FIG. 7 is a transmittance characteristic diagram showing the relationship between the wavelength of light transmitted through the liquid crystal light valve 22 and the transmittance when the in-plane retardation of the C plate 92 is varied from 0 to 8 nm.
In FIG. 7, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance. In the figure, P ₀ means a polarizer, which is a transmittance characteristic of only the polarizing plates 93 and 94 and shows an ideal transmittance characteristic.

As shown in FIG. 7, when the in-plane retardation is 0 nm, in the case of only the liquid crystal layer 80 in other words, while the thus separated from the polarizer P _0, polarizer P in the case plane retardation of 7nm _A transmittance characteristic close to ₀ is obtained.

As described above, in this embodiment, the same effect as that of the first embodiment described above can be obtained.
Further, although the phase difference of the liquid crystal layer 80 when a non-selection voltage is applied, the so-called residual phase difference is increased, the liquid crystal molecules are easily tilted when a selection voltage is applied, and resistance to a lateral electric field can be obtained. And the response is faster.

In the first and second embodiments described above, the case where the in-plane retardation of the C plate 92 is 3 to 5 nm and the case of 7 nm have been described. However, the in-plane retardation may be 20 nm or less. For example, the value is not limited.
The reason for this is that the vertical alignment liquid crystal whose pretilt is less than 80 ° causes a decrease in contrast and makes it difficult to obtain a good display. Therefore, in order to obtain a high-contrast display, it is preferable that the pretilt is higher than 80 °. The in-plane retardation of the C plate 92 necessary to compensate for the retardation of such vertically aligned liquid crystal having a pretilt of 80 ° or more is 20 nm. Therefore, the in-plane retardation of the C plate 92 is preferably 20 nm or less.

  In the first and second embodiments described above, a configuration in which one C plate 92 is provided is employed, but a configuration in which a plurality of C plates 92 are provided may be employed. In this case, it is preferable to adjust so that the sum of the in-plane phase differences of each of the plurality of C plates 92 is close to the value of the polarizer shown in FIGS.

  In addition, the technical scope of the present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention. For example, in the embodiment, a liquid crystal light valve including a TFT as a switching element has been described as an example, but a two-terminal element such as a thin film diode may be adopted as the switching element. In the embodiment, the description has been given of the three-plate projection display device including the transmissive liquid crystal light valve as an example. However, the present invention can be applied to a single-plate projection display device or a direct-view display device.

The block diagram which shows the principal part of the projection type display apparatus of this invention. FIG. 3 is an equivalent circuit diagram of a liquid crystal panel in the projection display device of the present invention. Explanatory drawing of the planar structure of the liquid crystal panel in the projection type display apparatus of this invention. Explanatory drawing of the cross-sectional structure of the liquid crystal panel in the projection type display apparatus of this invention. The disassembled perspective view of the liquid crystal light valve in the projection type display apparatus of this invention. The figure which shows the transmittance | permeability characteristic of 1st Embodiment in the projection type display apparatus of this invention. The figure which shows the transmittance | permeability characteristic of 2nd Embodiment in the projection type display apparatus of this invention.

Explanation of symbols

22, 23, 24 Liquid crystal light valve (light modulation means), 52 alignment film, 80 liquid crystal layer, 92 C plate (optical compensation plate), 93 polarizing plate (first polarizing plate), 94 polarizing plate (second polarizing plate) , PJ Projection type display device

Claims (5)

When the refractive indexes in two azimuth directions perpendicular to each other in the plane are defined as nx and ny, and the refractive index in the thickness direction is defined as nz, the optical axis satisfies nz <nx and nz <ny. , An optical compensator having an in-plane retardation satisfying nx>ny;
A light modulation means comprising a liquid crystal layer with negative dielectric anisotropy having a pretilt in an azimuth direction substantially perpendicular to the direction of the slow axis of the in-plane retardation;
A projection-type display device comprising:   The projection display device according to claim 1, wherein the in-plane retardation is 20 nm or less.   The projection display device according to claim 1, wherein the alignment film for aligning the liquid crystal layer is made of an inorganic material. The light modulating means includes a first polarizing plate provided on the light incident side of the liquid crystal layer and a second polarizing plate provided on the light emitting side of the liquid crystal layer,
The optical compensator is disposed between the liquid crystal layer and the first polarizing plate, or between the liquid crystal layer and the second polarizing plate. Any one of the projection type display apparatuses. The projection display apparatus according to claim 1, wherein an antireflection film is formed on a surface of the optical compensation plate.

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